1. Field of the Invention
This invention relates to automatic, multi-station die casting machines and more particularly to a three bar, horizontal, rotary die casting machine for casting rotors or the like.
2. Description of the Prior Art
Conventional die casting machines include stationary front and back plates and a movable plate reciprocably mounted between the two plates. The relative positions of the plates are maintained by a plurality of tie bars extending between the plates. Die halves are fastened to the front plate and the traveling plate, respectively, and the traveling plate is extended and retracted to open and close the die. When the die is closed, molten metal is injected into the die to form a part.
After the part is formed, the traveling plate is retracted and the die is opened. After the die has been opened a predetermined distance, bumper pins slidably mounted in openings in the die and traveling plate, engage a bumper plate behind the traveling plate. These pins engage and eject the part from the portion of the die attached to the traveling plate.
After the part is removed from the die casting machine, the excess metal, generally referred to as the sprue or runner system, is removed from the part in a separate pressing machine called a trim press.
A more efficient die casting machine incorporates the trimming operation in the die casting machine. In this type of machine, an indexing apparatus rotates the part between a casting station and a trimming station in the same die casting machine. For forming conventional cast parts, the cast part is usually attached to the indexing mechanism by the sprue created in the formation of the part. The part is then rotated to a trimming station where the part is removed and then to a subsequent location where the spue is removed. In die casting machines that are employed for casting parts wherein molten metal is injected into a pre-formed part body inserted into the machine, the part body is inserted into a carrier plate attached to the indexing mechanism at a loading station, and the carrier plate carries the part to the various stations.
One particular type of application involving a pre-formed part body is the casting of a rotor for an electrical motor. In this type of application, the part body comprises a series of circular plates or laminations connected together by a temporary skew pin inserted through an opening in center of the laminations. Die casting machines are employed for casting connector bars and end rings in the rotor assembly. The indexing apparatus first picks up the rotor body at a loading station and then moves it to a casting station where the connector bars and end rings are formed. The rotor is then carried through a cooling station, after which time the temporary skew pins are ejected from the cast rotor. Finally, the rotor is removed from the machine. At some point, the sprue or runner system is removed from the part and returned to a waste container for reuse. The entire procedure is automatic.
In most die casting machines, molten material, usually zinc, aluminum, or magnesium, is injected into the die in one of two ways. In one method, the molten metal is conveyed outwardly and injected into the side of the die cavity, leaving a runner attached to the side of the cast part. In another method, the molten metal is injected into the ends of the die cavity through inwardly tapered cone-shaped openings in the die plate, with the openings having a small diameter on the side of the die plate adjacent the interior of the die cavity. This process is called "pin-point gating" because the runner system is attached to the molded part only by means of narrow necks or "pin-points" of molded material, which can be broken away easily in removing the runner system from the cast part. Pin-point gating also provides an advantage in casting rotors in that it makes it possible to inject the molded metal directly into the die in the direction in which it will flow in molding the part.
It is an object of the present invention to provide an improved automatic die casting machine that is particularly suitable for casting rotors or stators or other such products wherein a part body is loaded into the machine and a casting is formed in the part body.